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Design and analysis

Plans move forward for Boston viaduct replacement

Transport officials in the US state of Massachusetts are analysing options for the replacement of a deteriorated viaduct carrying the I-90 highway in Boston.

The Allston Viaduct, which was constructed during the 1960s, is nearing the end of its useful life and costs about US$800,000 a year to maintain. Leaders of the Massachusetts Department of Transportation (MassDOT) and Massachusetts Bay Transportation Authority (MBTA) have received an update on the project to replace the viaduct, which carries several lanes of highway traffic over Boston’s Allston neighbourhood into and out of downtown Boston.

Three replacement options have been discussed, including replacing the viaduct and keeping the area's railway at-grade; putting the railway on a viaduct and building an at-grade highway; or putting both at-grade. Costs have been put at between US$500m and US$1bn.

The project’s design is approximately 15% complete and the current schedule for calls for the completion of the project’s preliminary design in 2019 ready to begin the process to procure a contractor. Construction work and related activities would then be expected to begin in 2020.

“The focus of MassDOT is moving the project forward now so the essential elements can be built to replace the deteriorated viaduct carrying the highway vehicles,” said transportation secretary and CEO Stephanie Pollack. “With the highway viaduct replacement, there is an opportunity to do additional ‘enhancements’ to the interchange to benefit drivers on local roads, pedestrians and cyclists, but those ‘enhancements’ cannot be committed to until after a finance plan for the project is confirmed.”

Chief highway engineer Patricia Leavenworth said that the Allston Viaduct is a complex structure that impacts all modes of transportation throughout the area including vehicles traveling on I-90, local traffic, MBTA commuter rail and Amtrak trains, as well as those who are travelling by bicycles or on foot. “The viaduct is structurally deficient and showing signs of deterioration and on a yearly basis, MassDOT spends on average US$800,000 to maintain the viaduct. The time has come to move this project forward through the design phase so it can be rebuilt,” she said.